The real audience for President Obama's State of the Union speech

President Obama delivers his State of the Union address on Capitol Hill… (Pablo Martinez Monsivais…)

The news coverage about President Obama's State of the Union speech Tuesday suggests that he's going to take the same tone as in his second inaugural address, advancing an unapologetically left-of-center agenda that, according to Obama, has broad public support.

There's nothing novel about a State of the Union speech that provides a heaping helping of red meat for the faithful, even if it's often decorated with bipartisan bunting. Regardless of how genial the tone may be, the speech isn't typically aimed at currying favor among lawmakers on the other side of the aisle. It's about taking advantage of the unusually bright spotlight provided by all the major broadcast TV networks and cable news outlets.

You might think that no one really pays attention to these affairs. Many may recall Supreme Court Justice Samuel A. Alito Jr. shaking his head when Obama criticized the Citizens United ruling in 2010, but the last truly memorable point made by a president at a State of the Union speech probably was President George W. Bush's "axis of evil" comment in 2002.

Nevertheless, these speeches command an extremely large audience, if for no other reason than that they preempt the prime-time lineup at all four of the major over-the-air networks and the two biggest Spanish-language broadcasters. According to Nielsen, each of Obama's four previous State of the Union addresses (including the one in 2009 that wasn't technically a State of the Union) drew at least 38 million viewers. Those are well short of the Super Bowl's numbers, but they dwarf the ratings for the most popular regularly scheduled shows, such as "NCIS" on CBS and "American Idol" on Fox.

Given access to so many American homes, presidents understandably use the speech to try to build grass-roots support for their agendas. It's safe to expect Obama to talk about jobs, infrastructure repairs, higher education, gun control, immigration reform, energy independence and troop withdrawals from Afghanistan. He'll also likely expand on his radio address Saturday, which called for replacing the coming "sequester" -- automatic across-the-board spending cuts of about $85 billion -- with tax hikes and smaller, targeted spending cuts.

There's bipartisan interest in aspects of just about all of these items, but the two parties diverge (and often sharply so) about the right steps to achieve them. The split has been particularly clear on fiscal issues, where Democrats have insisted on tax increases as part of any budget deal, while Republicans have demanded spending cuts and limits on entitlements.

Obama isn't relying just on TV to help rally public support. The White House also will use the Internet to carry his speech enhanced with charts and graphics. And Organizing for Action, the policy advocacy group formed from the erstwhile Obama for America campaign machine, is using the speech as a rallying point for a new grass-roots lobbying push.

The challenge for Obama will be persuading Congress to broaden its focus beyond the budget fights that have consumed so much of its energy. The president is trying yet again to persuade lawmakers to sign onto a "grand bargain" that shrinks the deficit enough in the coming years to stop the national debt from growing faster than the economy. His hope is that the deep defense cuts called for by the sequester will bring the two sides together after two years of intermittent and unavailing talks. But many conservative Republicans have come to accept the sequester as a sure way to reduce discretionary spending by $1.2 trillion over 10 years. For them, the issue isn't how to avoid the sequester, it's how to parlay it into cuts in entitlement programs.

Obama has made no secret of his plan to use the bully pulpit to try to persuade Republicans to move in his direction on policy disputes. Tuesday's speech will be his latest effort to do just that. And it's clear that he needs the public help to move anything through the Capitol's highly polarized chambers. If he can't persuade Republicans to sign a deal that puts the fiscal fighting behind them, chances are good that the rest of the agenda he lays out Tuesday won't go anywhere either.